Hot melt adhesives for elastic attachment application generally contain 20-35% polymer. Such polymer content results in high viscosity, and thus the typical application temperature is 325° F. (160° C.) or greater. To reduce the energy demands and glue burn-through (hot adhesive partially or completely melts the polymeric substrate) as well as the occupational risks associated with applying hot melt adhesives, there is a need to provide adhesives that are suitable for hot melt applications at lower temperatures. Decreasing the application temperature of the adhesives, however, often leads to negative cohesion and creep resistance of the adhesive.
WO 2007/047232 is directed to a low application temperature hot melt adhesive by utilizing a high softening point mid-block tackifier with SIS copolymer that has 14-35 wt % styrene content and molecular weight of about 100,000 to 200,000 or SBS copolymer that has 20-45 wt % styrene content and molecular weight of about 50,000 to 120,000. The use of high softening point mid-block tackifiers leads to higher viscosity, which limits the application temperature greater than 130° C. Lowering the viscosity with lower softening point mid-block tackifiers, however, leads to negative creep resistance of the adhesive.
There continues to be a need in the art for low application temperature hot melt adhesives, with desirable cohesion and creep resistance. Such attributes would make the adhesive particularly well-suited for use in the manufacture of elastic attachment adhesive. The current invention addresses this need.